P. K. Freeman, D. M. Balls and D. J. Brown, J. Org. Chem. 33,2211 (1968) (see also the publications 10 and 15 cited in S. Ranganathan, D. Ranganathan and A. K. Mehrotra, Syntheses 1977, 289) already described the synthesis of racemic mixtures of bicyclo[2.2.2]oct-5-en-2-ones starting from substituted cyclohexa-1,4-dienes. Similarly, I. Alfaro, W. Ashton, K. L. Rabone & N. A. J. Rogers, Tetrahedron, 30, 559 (1974) and R. P. Gregson & R. N. Mirrington, Chem. Commun. 1973, 598, described substituted bicyclo[2.2.2]oct-5-en-2-ones using 2-acetoxy- or 2-chloroacrylonitriles as ene component.
The enrichment of an enantiomer has been described heretofore only by K. Mislow & J. G. Berger, Z. Am. Chem. Soc., 84, 1956 (1962) through recrystallization of ephedrine salts. This enrichment resulted in an about 40% optical purity.
The photochemical conversion of racemates of bicyclo[2.2.2]oct-5-en-2-ones to form racemic tricyclo[3.3.0.0.sup.2,8 ]octan-3-ones of bicyclo[4.2.0]octenones was described by R. S. Givens, W. F. Oettle, R. L. Coffin & R. G. Carlson, J. Am. Chem. Soc. 93, 3957 (1971). The photochemical conversion of racemates of bicyclo[2.2.2]oct-5-en-2-ones was also reported by C. Carter, S. Chandrasekhar, M. Demuth, K. Nakano & K. Schaffner in Contributed Paper No. 39 of the IUPAC VIII/1980 in Seefeld, Austria.
The racemic bicyclo[2.2.2]oct-5-en-2-ones having been described contain only H and one methyl group as substituents.